U.S. patent application number 11/488133 was filed with the patent office on 2007-02-01 for image forming apparatus.
This patent application is currently assigned to Brother Kogyo Kabushiki Kaisha. Invention is credited to Atsushi Kato, Hirotaka Mori.
Application Number | 20070025762 11/488133 |
Document ID | / |
Family ID | 37203181 |
Filed Date | 2007-02-01 |
United States Patent
Application |
20070025762 |
Kind Code |
A1 |
Kato; Atsushi ; et
al. |
February 1, 2007 |
Image forming apparatus
Abstract
An image formation apparatus is provided that prevents a belt
from becoming displaced or detached from a belt unit. When a belt
unit is detached from a main body casing, a tension roller is fixed
in an outwardly protruding position by a fixing member. Thereby,
the conveyor belt is stretched such that the conveyor belt is
configured to be prevented from becoming displaced or detached.
When the belt unit is mounted in the main body casing, fixation of
the tension roller by the fixing member is released by a releasing
protrusion and a suitable operating tensile force is imparted to
the conveyor belt by coiled springs provided on the main body
casing side.
Inventors: |
Kato; Atsushi;
(Ichinomiya-shi, JP) ; Mori; Hirotaka;
(Ichinomiya-shi, JP) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.;ATTORNEYS FOR CLIENT NOS. 0166889, 006760
1001 G STREET, N.W., 11TH FLOOR
WASHINGTON
DC
20001-4597
US
|
Assignee: |
Brother Kogyo Kabushiki
Kaisha
Nagoya-shi
JP
|
Family ID: |
37203181 |
Appl. No.: |
11/488133 |
Filed: |
July 18, 2006 |
Current U.S.
Class: |
399/121 |
Current CPC
Class: |
G03G 15/1615 20130101;
G03G 2215/00139 20130101; G03G 15/161 20130101; G03G 15/754
20130101; G03G 2221/1642 20130101 |
Class at
Publication: |
399/121 |
International
Class: |
G03G 15/16 20060101
G03G015/16; G03G 21/16 20060101 G03G021/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 26, 2005 |
JP |
JP2005-216178 |
Claims
1. An image forming apparatus comprising: a belt unit includes a
belt, a plurality of rollers supporting the belt, and a frame
rotatably supporting the rollers; and an apparatus main body in
which the belt unit is detachably mounted; wherein the belt unit
comprises: a securing member disposed at an inner surface side of
the belt and configured to impart a tensile force to the belt when
the belt unit is detached from the apparatus main body.
2. The image forming apparatus according to claim 1, wherein the
apparatus main body comprises: a tension imparting device that
imparts an operating tensile force to the belt of the belt unit in
a mounted state.
3. The image forming apparatus according to claim 2, wherein the
belt unit comprises: an urging device that imparts the tensile
force to the belt by generating an urge that applies an outward
force to the securing member in a state in which the belt unit is
detached from the apparatus main body.
4. The image forming apparatus according to claim 3, wherein the
tensile force imparted to the belt by the urging device is less
than the operating tensile force that is imparted to the belt by
the tension imparting device.
5. The image forming apparatus according to claim 3, wherein the
apparatus main body comprises: an urge releasing device that
releases the urge generated by the urging device in a state in
which the belt unit is mounted in the apparatus main body.
6. The image forming apparatus according to claim 5, wherein the
urge releasing device releases the urge generated by the urging
device occurring with an operation to mount the belt unit in the
apparatus main body.
7. The image forming apparatus according to claim 1, wherein the
belt unit comprises: a fixing device configured to fix the securing
member in an outwardly projecting position in a state in which the
belt unit is detached from the apparatus main body.
8. The image forming apparatus according to claim 7, wherein the
apparatus main body comprises: a fixation releasing device that
releases the fixation of the fixing device in a state in which the
belt unit is mounted in the apparatus main body.
9. The image forming apparatus according to claim 8, wherein the
fixation releasing device releases the fixation by the fixing
device occurring with an operation to mount the belt unit in the
apparatus main body.
10. The image forming apparatus according to claim 2, wherein the
securing member comprises: a tension roller that imparts the
operating tensile force to the belt via the tension imparting
device in a state in which the belt unit is mounted in the
apparatus main body.
11. The image forming apparatus according to claim 2, wherein the
securing member comprises: a transfer roller that is disposed
opposite an image bearing device provided in the apparatus main
body such that the belt is positioned between the transfer roller
and the image bearing device; and wherein the transfer roller
transfers a developer image that is carried on the image bearing
device via application of a transfer bias between the image bearing
device and the transfer roller.
12. The image forming apparatus according to claim 2, wherein the
apparatus main body comprises: a cleaning roller that contacts
against an outer surface of the belt; and wherein the securing
member comprises a cleaner backup roller that is disposed opposite
to the cleaning roller to position the belt between the cleaner
backup roller and the cleaning roller.
13. The image forming apparatus according to claim 1, wherein the
belt comprises: a protruding guide rib on an inner surface that
engages with the rollers to inhibit skewing of the belt.
14. An image forming apparatus including a belt unit detachably
mounted to an apparatus main body and comprising a belt, a
plurality of rollers supporting the belt in a stretched state, and
a frame rotatably supporting the rollers, and also including a
tension imparting device that imparts an operating tensile force to
the belt of the belt unit in a mounted state, wherein the belt unit
comprises: a plurality of securing members located along an inner
surface side of the belt that impart a tensile force to the belt
when the belt unit is detached from the apparatus main body.
15. The image forming device of claim 14 wherein each of the
plurality of securing members comprises a transfer roller
positioned opposite to a photosensitive drum of one of a
corresponding plurality of development cartridges via the belt when
the belt unit and the plurality of development cartridges are in a
mounted condition.
16. The image forming device of claim 14 wherein each of the
plurality of securing members imparts the tensile force to the belt
via a corresponding plurality of urging devices; wherein the image
forming device comprises an operation part that engages said each
of the plurality of urging devices when the belt unit is mounted to
the image forming device; and wherein the operation device is
actuated to release the tensile force generated by the plurality of
urging devices.
17. The image forming device of claim 16, wherein each of the
plurality of urging devices comprises a first resilient member and
a second resilient member; wherein each of the second resilient
members generate a contact force; wherein the first resilient
members and the second resilient members generate the tensile
force; and wherein the contact force presses the belt between each
of the transfer rollers and a photosensitive drum of each of a
corresponding plurality of development cartridges.
18. An image forming device comprising a belt unit detachably
mounted in an apparatus main body and including a belt, a plurality
of rollers supporting the belt in a stretched state, and a frame
rotatably supporting the rollers, wherein the belt unit comprises:
a securing member disposed at an inner surface side of the belt and
configured to impart a tensile force to the belt when the belt unit
is detached from the apparatus main body; wherein the image forming
device includes a tension imparting device that imparts an
operating tensile force to the belt of the belt unit when the belt
unit is attached to the apparatus main body; wherein the securing
member is a backup roller that imparts the tensile force via a
change of position in a tension inducing direction with respect to
the belt due to an urging of an urging device.
19. The image forming device according to claim 18 comprising an
urge releasing device that releases the tensile force when the belt
unit is attached to the apparatus main body.
20. The image forming apparatus according to claim 19, wherein the
belt comprises: a protruding guide rib on an inner surface that
engage with the rollers to guide the belt.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from Japanese Patent
Application No. 2005-216178 filed Jul. 26, 2005. The entire content
of this priority application is incorporated herein by
reference.
TECHNICAL FIELD
[0002] The disclosure relates to an image forming apparatus such as
a laser printer, and more particularly to an image forming
apparatus equipped with a detachable belt unit.
BACKGROUND
[0003] Conventionally, an image forming apparatus is known such as
a laser printer that uses a belt for conveying sheets, performing
intermediate transferring, and the like. In general, this type of
belt (in the form of a belt unit) can be detached from the main
body of the apparatus in order to enable the replacement or repair
of the belt, typically after a predetermined period of use.
[0004] Normally, the belt unit is provided with a tension imparting
component comprising a coiled spring or the like. The tension
imparting component imparts a tensile force to the belt by urging a
tension roller in an outward direction. The tension roller supports
the belt and can change position in an inward or outward
direction.
[0005] In contrast thereto, Japanese Laid-Open Patent No.
2001-209294 discloses an apparatus in which a tension imparting
component is provided on the main body side of the apparatus. This
tension imparting component is configured so that a predetermined
tensile force is imparted to the belt. This is as a result of the
tension imparting component urging the tension roller outward when
the belt unit is mounted in the apparatus main body. In this
apparatus, the structure of the belt unit is simplified because the
tension imparting component is not provided in the belt unit.
[0006] In the configuration such as that of the previously
described Japanese Laid-Open Patent No. 2001-209294, the belt has
conventionally been formed of a hard material such as
polyamide-imide. Therefore, changes in the peripheral length of the
belt were relatively small. As a result, it was sufficient for the
tension roller to have a relatively small moveable range. The belt
did not slacken significantly even when the belt unit was detached
from the apparatus main body.
[0007] Recently however due to demands for greater durability,
there is an increasing use of belts that are made of a material
that is more flexible than the conventional belt. Although this
type of belt provides greater durability than a conventional belt
material, such as polyamide-imide, belt elongation and changes in
the peripheral length of the belt due to thermal expansion have
increased.
[0008] When the use of a belt made of this kind of flexible
material was attempted in the apparatus disclosed in the previously
described Japanese Laid-Open Patent No. 2001-209294, it was
necessary to increase the moveable range of the tension roller in
order to correspond to the changes in the peripheral length of the
belt. As a result, there was a problem such that the slackening of
the belt increased when the belt unit was detached from the
apparatus main body. Therefore, the belt was liable to be displaced
along a width direction (axial direction of the rollers) and become
detached from the belt unit.
SUMMARY
[0009] At least some aspects of the present invention relate to
preventing a belt from becoming displaced or detached from a belt
unit. In order to achieve the above object, an image forming
apparatus according to an aspect of the invention is provided
comprising a belt unit having a belt, a plurality of rollers
supporting the belt in a stretched state, and a frame rotatably
supporting the rollers. In addition there is an apparatus main body
in which the belt unit is detachably mounted, and which has a
tension imparting device that imparts an operating tensile force to
the belt when mounting the belt unit.
[0010] The belt unit is provided with a securing member disposed on
an inner surface side of the belt that is configured to change
position in a tension inducing direction (e.g., an inner or outer
direction) with respect to the belt. The securing member stretches
the belt by projecting outwardly in a state in which the belt unit
is detached from the apparatus main body. Since the belt is
stretched by the securing member projecting outward when the belt
unit is detached from the apparatus main body, it is possible to
inhibit the belt from becoming displaced or detached.
[0011] According to another aspect of the invention, an image
forming apparatus is provided according to a previous aspect in
which guide ribs are provided in a protruding condition on an inner
surface of the belt. The guide ribs engage with the rollers to
inhibit skewing of the belt.
[0012] In a case where guide ribs for skew prevention are provided
on the inner surface of a belt, for example, in a replacement belt
unit or the like, there is a risk of the guide ribs overriding the
rollers and dropping off when the belt slackens and is axially
(horizontally) displaced in a state in which tension is not
imparted to the belt.
[0013] If the belt unit is mounted in a state in which the guide
ribs are not properly located, and an operating tensile force is
imparted to the belt by a tension imparting device, a difference in
the level of the outer surface of the belt is produced at the
boundary between the region in which the belt directly contacts the
roller surface and the region in which the belt contacts the roller
surface via the rib. This creates the possibility that a stress
concentration may be produced in this portion of the belt and
subsequently damage the belt.
[0014] In contrast, according to the present structure, since the
belt is stretched by the outward projection of the securing member
when the belt unit is detached from the apparatus main body, the
state is maintained in which the guide ribs are engaged with the
rollers. Consequently, the previously described stress
concentration and possible damage to the belt is prevented.
[0015] In an aspect of the current invention, an image forming
apparatus includes a belt unit detachably mounted to an apparatus
main body. The belt unit comprises a belt, a plurality of rollers
supporting the belt in a stretched state, and a frame rotatably
supporting the rollers. The image forming apparatus also includes a
tension imparting device that imparts an operating tensile force to
the belt of the belt unit in a mounted state.
[0016] The belt unit also comprises a plurality of securing members
located along an inner surface side of the belt. The plurality of
securing members imparts a tensile force to the belt when the belt
unit is detached from the apparatus main body. The plurality of
securing members imparts the tensile force via a change position in
an inner or outer direction with respect to a circumference of the
belt.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Illustrative aspects in accordance with the invention will
be described in detail with reference to the following figures
wherein:
[0018] FIG. 1 is a side sectional view showing a schematic
configuration of a laser printer according to an aspect of the
present invention;
[0019] FIG. 2 is a side sectional view of the laser printer in a
state in which the belt unit was detached therefrom;
[0020] FIG. 3A is a partial enlarged plan view of the belt unit
that shows a state in which the conveyor belt is stretched
normally;
[0021] FIG. 3B is a partial enlarged plan view of the belt unit
that shows a state in which the conveyor belt has separated from
the roller;
[0022] FIG. 4 is a side sectional plan view showing the state of
the belt unit prior to mounting;
[0023] FIG. 5 is a side sectional plan view showing the state of
the belt unit after mounting;
[0024] FIG. 6A is a partial enlarged side view showing the state of
the belt unit prior to mounting;
[0025] FIG. 6B is a partial enlarged side view showing the state of
the belt unit after mounting;
[0026] FIG. 7 is a partial enlarged side sectional view showing the
state of a belt unit prior to mounting, according to another
aspect;
[0027] FIG. 8 is a partial enlarged side sectional view showing the
state of the belt unit of FIG. 7 after mounting;
[0028] FIG. 9 is a partial enlarged side sectional view showing the
state of a belt unit prior to mounting according to an additional
aspect;
[0029] FIG. 10 is a partial enlarged side sectional view showing
the state of the belt unit of FIG. 9 after mounting;
[0030] FIG. 11 is a side sectional view showing a schematic
configuration of a laser printer according to a further aspect;
and
[0031] FIG. 12 is a side sectional view of the laser printer in a
state in which the belt unit of FIG. 11 was detached therefrom.
DETAILED DESCRIPTION
[0032] An aspect of the image forming apparatus will now be
described with reference to FIGS. 1 to 6.
(Overall Structure of the Image Forming Apparatus)
[0033] FIG. 1 is a side sectional view showing the schematic
configuration of a laser printer 1 as an illustrative aspect of the
image forming apparatus. FIG. 2 is a side sectional view of the
laser printer 1 showing the state in which process cartridges 26
and a belt unit 15 are detached therefrom. In the following
description, the right side in FIG. 1 is taken as the front
side.
[0034] The laser printer 1 is a direct transfer type tandem color
laser printer comprising, as shown in FIG. 1, a substantially
rectangular main body casing 2 (corresponding to an example of the
apparatus main body). A top cover 3 is provided on the top surface
of the main body casing 2. The top cover 3 is capable of opening
and closing. It is possible to exchange the process cartridges 26
and/or the belt unit 15 located inside the main body casing 2 by
opening this top cover 3, as shown in FIG. 2. On the upper surface
of the top cover 3 is formed a discharge tray 5 on which sheets 4
are stacked after image formation.
[0035] A sheet supply tray 7 is mounted in the lower part of the
main body casing 2 in a condition in which it can be drawn out
towards the front of the laser printer 1. The sheets 4 for forming
images are loaded in the sheet supply tray 7. A sheet pressing
plate 9 and a spring 8 are arranged within the sheet supply tray 7.
The sheet pressing plate 9 can tilt so as to lift the front end
side of the sheets 4 through the urging of the spring 8.
[0036] A pickup roller 10 and a separation pad 11 are provided at
an upper position at the front end of the sheet supply tray 7. The
separation pad 11 is pressed against the pickup roller 10 through
the urging of an unshown spring. Further, a pair of sheet feeding
rollers 12 is provided at a slanting position that is forward and
upward of the pickup roller 10. A pair of registration rollers 13
is further provided upward of the pair of sheet feeding rollers
12.
[0037] The uppermost sheets 4 in the sheet supply tray 7 are
pressed toward the pickup roller 10 by the sheet pressing plate 9.
When the sheets 4 are sandwiched between the pickup roller 10 and
the separation pad 11, the uppermost sheets 4 are separated into
single sheets by the rotation of the pickup roller 10. A sheet 4,
which is delivered from between the pickup roller 10 and the
separation pad 11, is fed towards the registration rollers 13 by
the sheet feeding rollers 12. At the registration rollers 13, the
sheet 4 is delivered at a predetermined timing onto the belt unit
15.
[0038] The belt unit 15 is positioned to the rear of the
registration rollers 13 and is detachable from the main body casing
2. The belt unit 15 comprises a conveyor belt 18, which is
horizontally suspended between a pair of rollers 16 and 17. Each of
the rollers 16 and 17 is respectively disposed in a separated
condition at the front and rear of the belt unit 15. Of the pair of
rollers 16 and 17, the rear-side roller is a driving roller 17,
which is rotationally driven by the power of an unshown motor. The
front-side roller is a tension roller 16 (corresponding to an
example of a securing member) used to impart a tensile force upon
the conveyor belt 18, as described later.
[0039] The conveyor belt 18 is a belt composed of a resin material
such as polycarbonate. The conveyor belt 18 moves in a circulating
manner in a counter-clockwise direction, as viewed in FIG. 1, due
to the rotational driving of the driving roller 17. The movement of
the conveyor belt 18 conveys a sheet 4 that was delivered onto the
upper surface thereof.
[0040] Four transfer rollers 19 are disposed on an inner surface
side of the conveyor belt 18 opposing the photosensitive drums 31
(corresponding to examples of image bearing devices) of the process
cartridges 26, as described later. The four transfer rollers 19 are
provided along a line at fixed intervals in a front to rear
direction. The conveyor belt 18 is sandwiched between each transfer
roller 19 and a corresponding photosensitive drum 31. At the time
of an image transfer, a transfer bias is applied between the
relevant transfer roller 19 and the corresponding photosensitive
drum 31. The structure of the belt unit 15 is described in detail
later.
[0041] A cleaning roller 21 is provided on the underside of the
belt unit 15 for removing paper powder and toner or the like, which
may be attached to the conveyor belt 18. The cleaning roller 21
comprises a structure in which a foamed material comprising silicon
is provided around a shaft material made of metal. The cleaning
roller 21 is disposed opposite to a metal backup roller 22 arranged
within the belt unit 15, thereby sandwiching the conveyor belt 18.
Upon the application of a predetermined bias between the cleaning
roller 21 and the backup roller 22, any toner and the like located
on the conveyor belt 18 is electrically attracted to the side of
the cleaning roller 21.
[0042] A metal collection roller 23 is arranged so as to contact
the cleaning roller 21 and remove any toner and the like that may
be adhered to the surface thereof. Further, a blade 24 is arranged
so as to contact the collection roller 23 in order to scrape off
the toner and the like adhered to the surface thereof.
[0043] Four process cartridges 26, which correspond to the colors
magenta, yellow, cyan, and black, are respectively provided
side-by-side in the front to rear direction in a detachable
condition above the belt unit 15. A scanner portion 27 is provided
and is integrally attached to the top cover 3, on top of the
process cartridges 26. The scanner portion 27 irradiates a laser
beam L for each color onto the surface of the corresponding
photosensitive drum 31 by high speed scanning thereof, based on
predetermined image data.
[0044] The process cartridge 26 comprises a frame-shaped cartridge
frame 30, a scorotron charging device 32 and a photosensitive drum
31 arranged at the bottom of the cartridge frame 30, and a
development cartridge 34 that is detachably mounted onto the
cartridge frame 30.
[0045] The photosensitive drum 31 comprises a grounded metal drum
main body. The photosensitive drum 31 is formed by coating the
surface thereof with a positively charged photosensitive layer made
of polycarbonate or the like.
[0046] The scorotron charging device 32 is disposed facing the
photosensitive drum 31 in a position diagonally above the rear side
of the photosensitive drum 31. The scorotron charging device 32 is
spaced apart from the photosensitive drum 31 by a specified
interval so as to not come in contact therewith. The scorotron type
charging unit 32 is provided in order to uniformly and positively
charge the surface of the photosensitive drum 31 by generating a
corona discharge from a charging wire made of material such as
tungsten.
[0047] The development cartridge 34 is formed in a substantially
box shape. Inside of the development cartridge 34, a toner
containing chamber 38 is provided in the upper part thereof. A
supply roller 39, a developing roller 40, and a layer thickness
regulating blade 41, are provided in the lower part thereof. The
toner containing chambers 38 of each of the development cartridges
34 are respectively filled with a positive charging nonmagnetic
one-component toner of each of the colors yellow, magenta, cyan,
and black, as a developing agent. An agitator 42 is provided in
each toner containing chamber 38 for agitating the toner.
[0048] The supply roller 39 is formed by coating a metal roller
shaft with a conductive foam material. The developing roller 40 is
formed by coating a metal roller shaft with a conductive rubber
material. The toner, discharged from a toner containing chamber 38,
is supplied to the corresponding developing roller 40 via the
rotation of the supply roller 39. The toner is positively charged
at this time by friction between the supply roller 39 and the
developing roller 40. Further, the toner supplied onto the
developing roller 40 enters a space between the layer thickness
regulating blade 41 and the developing roller 40 occurring with the
rotation of the developing roller 40. The toner is thoroughly
further charged at this time due to friction and is supported as a
thin layer having a specified thickness on the surface of the
developing roller 40.
[0049] At the time of rotation, the surface of the photosensitive
drum 31 is initially charged uniformly and positively by the
scorotron charging device 32. Thereafter, the surface of the
photosensitive drum 31 is exposed by high-speed scanning of a laser
beam from the scanner portion 27, whereby an electrostatic latent
image is formed thereon that corresponds to an image to be formed
on the sheet 4.
[0050] Subsequently, when the positively charged toner, which is
carried on the developing roller 40, faces (opposes) and comes in
contact with the photosensitive drum 31 through the rotation of the
developing roller 40, the toner is supplied to the electrostatic
latent image formed on the surface of the photosensitive drum 31.
Thereby, the electrostatic latent image on the photosensitive drum
31 is visualized, and a toner image formed by reversal development
is carried on the surface of the photosensitive drum 31.
[0051] Thereafter, the toner images carried on the surfaces of each
photosensitive drum 31 are transferred in sequence to a sheet 4 due
to a negative transfer bias. The negative transfer bias is applied
to the transfer rollers 19 while the sheet 4, which is conveyed by
the conveyor belt 18, passes through each transferring position
between the corresponding transfer rollers 19 and photosensitive
drums 31. The sheet 4, onto which the toner images were transferred
to in this manner, is subsequently conveyed to a fixing device
43.
[0052] The fixing device 43 is disposed downstream (with respect to
the conveyance direction) of the conveyor belt 18, inside of the
main body casing 2. The fixing device 43 comprises a heat roller 44
that is rotationally driven. The heat roller 44 includes a heat
source such as a halogen lamp. A pressure roller 45 is disposed
below the heat roller 44 in such a way as to face and press against
the heat roller 44. The pressure roller 45 is rotated in accordance
with the rotational driving of the heat roller 44.
[0053] In the fixing device 43, the toner images are fixed to the
sheet 4 carrying the four colors of toner images by heating the
sheet 4 while the sheet 4 is being compressed and conveyed by the
heat roller 44 and the pressure roller 45. Thereafter, the sheet 4
(onto which the toner images were fixed by heating) is conveyed to
discharge rollers 47 that are provided in the upper part of the
main body casing 2. The sheet 4 is conveyed by a conveyance roller
46 disposed in a slanting manner downstream (with respect to the
conveyance direction) and upward of the fixing device 43. The sheet
4 is discharged onto the aforementioned discharge tray 5 by the
discharge rollers 47.
(Structure of a Belt Unit)
[0054] FIGS. 3A and 3B are plan cross-sections showing enlarged
views of a front end portion of the belt unit 15. FIG. 4 is a side
sectional view showing the state of the belt unit 15 prior to
mounting in the main body casing 2, and FIG. 5 is a side sectional
view showing the state of the belt unit 15 after mounting in the
main body casing 2. FIGS. 6A and 6B are side sectional views
showing the movement of a fixing member 55 prior to and after
mounting the belt unit 15 in the main body casing 2.
[0055] As shown in FIG. 4, the belt unit 15 comprises a belt frame
50 (corresponding to an example of the frame) made of synthetic
resin that is formed as a unit in a rectangular tabular shape. The
belt frame 50 includes a pair of side walls 50A respectively
disposed on the left and right sides of the belt frame 50. Bearing
devices 17A are mounted at each end of the shaft of the
aforementioned driving roller 17 and are supported at the rear of
each side wall 50A. The bearing devices 17A support the driving
roller 17 in a rotatable condition.
[0056] A slide member 51 is provided at the front end portion of
each side wall 50A. The slide member 51 can slide backward and
forward. Bearing devices 16A are mounted at each end of the shaft
of the tension roller 16 and are supported by the slide member 51.
As a result, the tension roller 16 is supported in a rotatable
condition and can change position within a predetermined range in
the forward and backward directions.
[0057] As shown in FIG. 3A, cylindrical guide collars 52 are
provided at each end of the tension roller 16 and the driving
roller 17. The outer surfaces of the cylindrical guide collars 52
are indented in a step-like shape. Guide ribs 53 are provided in a
protruding manner along the circumference of the conveyor belt 18,
at both side ends on the inner surface thereof.
[0058] In a state in which the tension roller 16 is in a position
approaching the outside (i.e., positioned away from the driving
roller 17), the conveyor belt 18 is tightly suspended between the
two rollers 16 and 17. In this state, each guide rib 53 engages
with the outer surface of the guide collars 52 of the tension
roller 16 and the driving roller 17 so as to prevent the skewing
(i.e., horizontal or axial displacement) of the conveyor belt
18.
[0059] Further, as shown in FIG. 3B, when the tension roller 16 is
at a position approaching the inside (i.e., positioned closer to
the driving roller 17) and slackness has been created in the
conveyor belt 18, the guide ribs 53 may float above the guide
collars 52 of the rollers 16 and 17 and become disengaged
therefrom. At this point, the conveyor belt 18 enters a state in
which it is liable to be displaced horizontally (i.e., along an
axial direction of the rollers 16 and 17).
[0060] As shown in FIG. 6A, a fixing member 55 (corresponding to an
example of a fixing device) is provided at a front end portion of
the side walls 50A in the belt frame 50. The fixing member fixes
the position of the tension roller 16. The fixing member 55 is made
of synthetic resin and integrally comprises a mounting shaft 55A
that extends in a horizontal direction (i.e., substantially
parallel to the axial direction of the roller 16), a fan part 55B
that extends towards the front from the mounting shaft 55A with a
substantially fan shape, and a guide shaft 55C that extends in a
horizontal direction from the lower end of the fan part 55B.
[0061] The fixing member 55 is rotatably supported around the
mounting shaft 55A. The guide shaft 55C passes through a groove 56,
which is provided in each side wall 50A. The fixing member 55 can
change position within a range from a fixation position, in which
the guide shaft 55C is positioned at the lower end of the groove 56
(see FIG. 6A), to a release position, in which the guide shaft 55C
is positioned at the upper end of the groove 56 (see FIG. 6B).
[0062] When the fixing member 55 is in the fixation position, the
leading end of the fan part 55B engages with a rear side of the
slide member 51 in order to fix the tension roller 16 in a location
toward the front end. In this state, the conveyor belt 18 is
suspended between the rollers 16 and 17 without significant
slackness (i.e., secured to the belt unit 15).
[0063] When the fixing member 55 is in the release position, the
fan part 55B recedes upward from the rear of the slide member 51.
The tension roller 16 then enters a state in which it can change
positions in the forward and backward directions. A spring 57 is
provided around the mounting shaft 55A. The fixing member 55 is
constantly urged towards the fixation position by this spring
57.
[0064] A roller shaft passage hole 58 is provided in each side wall
50A of the belt frame 50. The roller shaft 19A of a transfer roller
19 extends through the roller shaft passage hole 58. The roller
shaft passage hole 58 is formed in a substantially rectangular
shape. The dimensions of the roller shaft passage hole 58 in the
vertical and horizontal directions are configured to be greater
than the outer diameter of the roller shaft 19A. In a state where
the belt unit 15 is detached from the main body casing 2, the
roller shaft 19A is capable of changing positions in a diametrical
direction (vertical and forward and backward directions) within the
limits of the roller shaft passage hole 58.
(Structure Inside the Main Body Casing)
[0065] A main body frame (not shown) made of metal is provided
inside the main body casing 2. As shown in FIG. 4, unit support
parts 59 and 60 are made of synthetic resin and are used for
supporting each pair of ends of the driving roller 17 and the
tension roller 16. The unit support parts 59 and 60 are arranged in
pairs at the front and rear of the main body frame on the left and
right sides of the belt unit 15. The unit support part 60 at the
rear side is formed to be substantially in the shape of a letter C,
with an upward opening when viewed from a cross-sectional
perspective. In the opening thereof, a latch fitting 61, which is
formed in a V-shape when viewed in cross-section and is elastically
deformable, is provided in a condition in which the latch fitting
61 protrudes inward (i.e., to the right as viewed in FIGS. 4 and
5).
[0066] As shown in FIG. 5, the bearing device 17A, mounted at each
end of the driving roller 17, is inserted into the unit support
part 60. The driving roller 17 is retained in a positioned state
through the latching of each bearing device 17A by a corresponding
latch fitting 61. At the front side the unit support part 59 is
formed such that the upper surface thereof establishes a plane of a
fixed height along the forward and backward direction. The tension
roller 16 is supported in a state in which it is positioned in the
height direction by placing both bearing devices 16A, which are
mounted at each end of the tension roller 16, on a corresponding
unit support part 59.
[0067] A pair of levers 70 is provided inside of the main body
casing 2. The levers 70 can rotate around a rotating shaft 71. A
pair of coiled springs 72, which urge the respective levers 70 in a
clockwise direction (as viewed in FIGS. 4 and 5) (the levers 70 and
the coiled springs 72 correspond to examples of a tension imparting
device) are also provided inside of the main body casing 2.
[0068] When a bearing device 16A of the tension roller 16 is placed
on the front unit support part 59, the bearing device 16A presses
the top end of a lever 70 towards the rear. As a result, the
corresponding coiled spring 72 is placed in an extended state. The
bearing device 16A is urged towards the front by an elastic
restoring force thereof, thereby imparting a tensile force to the
conveyor belt 18.
[0069] Additionally, as shown in FIG. 6A, a releasing protrusion 73
(corresponding to an example of a fixation releasing device), is
provided inside of the main body casing 2. The releasing protrusion
73 displaces the guide shaft 55C of the fixing member 55 to an
upper side (i.e., the release position side) when mounting the belt
unit 15.
[0070] In the main body frame within the main body casing 2,
bearing members 63 are arranged in left and right side pairs
corresponding to each transfer roller 19. The bearing members 63
are used for supporting the roller shafts 19A of the transfer
rollers 19. Each bearing member 63 comprises a bearing groove 64
having a grooved shape that opens upward.
[0071] By inserting an end of the roller shaft 19A into the bearing
groove 64 from an upward direction, the roller shaft 19A can be
supported in a freely rotatable condition. At the edges of the
opening of the bearing groove 64, guide surfaces 65 are formed to
aid in guiding the roller shaft 19A into the bearing groove 64.
[0072] Each bearing member 63 is arranged so that it can change
position in a vertical direction. In addition, each bearing member
63 is retained in a positioned state with respect to the main body
frame in the cross and longitudinal directions. A spring 66 is
provided on the underside of each bearing member 63 and urges the
corresponding bearing member 63 in an upward direction.
(Operations When Attaching and Detaching the Belt Unit)
[0073] When exchanging the conveyor belt 18 or the like, as shown
in FIG. 2, the belt unit 15 is taken out from the main body casing
2 in a state in which the top cover 3 is opened and the process
cartridges 26 are removed. As shown in FIG. 6A, when the belt unit
15 is removed from the main body casing 2, the fixing member 55
shifts to a fixation position due to the urging of the spring 57,
and latches to the rear side of the slide member 51. As a result,
the tension roller 16 is fixed in a position in which it projects
to the front. Therefore, the conveyor belt 18 is stretched between
the two rollers 16 and 17 in a state almost without any
slackness.
[0074] As shown in FIG. 4, to mount the belt unit 15 from a
detached state into the main body casing 2, the belt unit 15 is
lowered in a substantially horizontal position. The bearing devices
17A at both ends of the driving roller 17 are pushed into the
interiors of the unit support parts 60. In addition, the bearing
devices 16A at both ends of the tension roller 16 are placed on the
unit support parts 59. As a result, as shown in FIG. 5, the belt
unit 15 is held in a substantially horizontal position by the front
and rear unit support parts 59 and 60.
[0075] During this process, the roller shaft 19A of each transfer
roller 19 is guided by the respective guide surfaces 65 so as to
insert the two ends of the roller shaft 19A into the corresponding
bearing grooves 64 of the bearing members 63. Thus, each transfer
roller 19 is positioned with respect to the front and rear
directions.
[0076] The conveyor belt 18 is stretched by a predetermined
operating tensile force since the bearing devices 16A push the top
ends of the levers 70 rearward and are then urged forward by the
elastic restoring force of the coiled springs 72. Thereafter, the
transfer rollers 19 are also positioned with respect to the
vertical direction since the transfer rollers 19 are pushed
downward (against the urging force of the springs 66) by the
photosensitive drums 31 when the process cartridges 26 are mounted
above the belt unit 15.
(Advantages of This Aspect of the Image Forming Apparatus)
[0077] According to the present illustrative aspect described
above, when the belt unit 15 is detached from the main body casing
2, displacement or inadvertent detachment of the conveyor belt 18
may be prevented, since the conveyor belt 18 is stretched by the
outward projection of the tension roller 16. In addition, the
conveyor belt 18 is retained in a stretched state by using the
fixing member 55 to fix the tension roller 16 in a position in
which it projects outward.
[0078] The fixation of the tension roller 16 due to the fixing
member 55 is released by the releasing protrusion 73 when the belt
unit 15 is mounted in the main body casing 2. Therefore, a suitable
operating tensile force can be applied to the conveyor belt 18 by
the coiled springs 72 that are provided on the main body casing 2
side.
[0079] Furthermore, since the releasing protrusion 73 releases the
fixation of the tension roller 16 (due to the fixing members 55)
occurring with an operation to mount the belt unit 15 in the main
body casing 2, a separate operation to release the fixation of the
tension roller 16 is not required when mounting the belt unit 15,
thereby enhancing the workability of the system. Consequently, the
structure of the belt unit 15 is simplified since an existing
component such as the tension roller 16 comprises the securing
member that projects outward to stretch the conveyor belt 18 when
the belt unit 15 is detached from the main body casing 2.
[0080] However, if the conveyor belt 18 slackens and shifts
horizontally (i.e., in a axial direction of a roller) when guide
ribs 53 for skew prevention are provided on the inner surface of
the conveyor belt 18, there is a risk of the guide ribs 53
overriding the guide collars 52 and dropping or falling off. If the
belt unit 15 is mounted in this state and an operating tensile
force is imparted to the conveyor belt 18 by the coiled springs 72,
a difference in the surface level of the conveyor belt 18 is
produced at the boundary between the region in which the conveyor
belt 18 directly contacts a roller surface and the region in which
the conveyor belt 18 contacts a roller surface via one of the guide
ribs 53. This results in the possibility of a stress concentration
being generated that will damage the conveyor belt 18.
[0081] Conversely, according to the present configuration it is
possible to prevent or inhibit the aforementioned damage to the
conveyor belt 18. The state in which the guide ribs 53 are engaged
with the guide collars 52 is retained, since the conveyor belt 18
is stretched by the outward projection of the tension roller 16
when the belt unit 15 is detached from the main body casing 2.
<Additional Illustrative Aspect>
[0082] Another illustrative aspect of the image forming apparatus
will be described next with reference to FIGS. 7 and 8.
[0083] FIG. 7 is an enlarged partial side sectional view showing a
state in which a belt unit 80, according to this example structure,
is detached from the main body casing 2. FIG. 8 is an enlarged
partial side sectional view showing a state in which the belt unit
80 is mounted in the main body casing 2. In the following
description, structural differences are mainly described with
respect to the previous aspect. Components that have the same
functions as those of the previous aspect are denoted by the same
symbols. A duplicate description of these components is
omitted.
[0084] Instead of the fixing member 55 and the spring 57 of the
previous aspect, the belt unit 80 of the current aspect comprises
an urging device 81 for urging the backup roller 22 (corresponding
to an example of a securing member) in an outward direction. Two
urging devices 81 are disposed as a pair in positions on the left
and right ends of the backup roller 22. Each of the urging devices
81 respectively comprises a first supporting member 82, a second
supporting member 83, a spring 84, and a spring 85.
[0085] The first supporting member 82 is provided in a condition in
which it can rotate around a mounting shaft 82A, to a point below
the belt frame 50. The first supporting member 82 is urged in a
downward direction (i.e., a clockwise direction as viewed in FIGS.
7 and 8) by the spring 84.
[0086] One end of the second supporting member 83 is provided in a
condition in which it can rotate around the mounting shaft 82A of
the first supporting member 82. The other end (i.e., a free end
side) of the second supporting member 83 supports the backup roller
22 in a freely rotatable condition. The second supporting member 83
is urged in a downward direction (i.e., clockwise direction as
viewed in FIGS. 7 and 8) by a spring 85 that is provided between
the first supporting member 82 and the second supporting member 83.
In a state in which an external force is not applied to the second
supporting member 83, the second supporting member 83 contacts
against a stopper part 82B of the first supporting member 82.
[0087] In a state in which the belt unit 80 is detached from the
main body casing 2, as shown in FIG. 7, the backup roller 22 is
held in a position in which it projects downward further than the
underside of the belt frame 50 due to the urging device 81. In
addition, the backup roller 22 is pressed against the inner surface
of the conveyor belt 18 due to the urging of the spring 84. The
conveyor belt 18 thus placed into a state in which it is stretched
without any significant amount of slackness.
[0088] At this time, the slide members 51 that support the bearing
devices 16A of the tension roller 16 are pressed to the rear most
end positions of their range of movement by the conveyor belt 18. A
tensile force imparted to the conveyor belt 18 by the urging device
81 is made to be less than the operating tensile force imparted by
the coiled springs 72 when the belt unit 80 is mounted in the main
body casing 2. The tensile force of the urging device 81 is at
least of a magnitude at which the conveyor belt 18 does not
excessively slacken. In other words, the magnitude of the urging
device 81 is such that the guide ribs 53 do not lift up away from
the guide collars 52.
[0089] When mounting the belt unit 80 in the main body casing 2,
the cleaning roller 21 (provided inside of the main body casing 2)
contacts against the backup roller 22 via the conveyor belt 18. The
contact of the cleaning roller 21 during the mounting process
pushes up the backup roller 22. Furthermore, and similar to the
mounting operation of the belt unit 80, an urge releasing
protrusion 86 (corresponding to an example of an urge releasing
device) provided within the main body casing 2 contacts against the
lower end of the first supporting member 82 and pushes up the first
supporting member 82.
[0090] As shown in FIG. 8, when the belt unit 80 is mounted in the
regular position, the backup roller 22 enters into a state in which
it has nearly withdrawn to an upper side, with respect to the
bottom of the belt frame 50. The backup roller 22 presses against
the cleaning roller 21 as a result of urging by the spring 85.
Additionally, the urging of the urging device 81 is released with
respect to the conveyor belt 18. Since the bearing devices 16A of
the tension roller 16 receive the elastic restoring force of the
coiled springs 72, as previously described, and are urged toward
the front side, a predetermined operating tensile force is imparted
to the conveyor belt 18.
[0091] According to the current illustrative aspect, since the
backup roller 22 is urged outward by the urging device 81, a
tensile force is imparted to the conveyor belt 18 so that the
conveyor belt 18 is held in a stretched state when the belt unit 80
is removed.
[0092] Since the tensile force imparted to the conveyor belt 18 by
the urging device 81 is weaker than the operating tensile force
imparted by the coiled springs 72 provided on the main body casing
2 side, the structure of the belt unit 80 can be simplified in
comparison to a case in which an urging device is provided that
imparts a tensile force to the belt unit 80 that is equal to the
operating tensile force of the coiled spring 72. More specifically,
for example, the rigidity of the belt frame 50 may be reduced,
thereby enabling miniaturization of the belt unit 80.
[0093] An appropriate operating tensile force is imparted to the
conveyor belt 18 by the coiled springs 72 since an urge generated
by the urging device 81 is released by the urge releasing
protrusion 86 when the belt unit 80 is mounted in the main body
casing 2. Additionally, a separate operation to release the urging
is not required since the urge releasing protrusion 86 releases the
urging of the urging device 81 occurring with an operation to mount
the belt unit 80. The workability of the image forming apparatus is
thereby enhanced. The structure of the belt unit 80 is simplified
since the securing member that projects outward to stretch the
conveyor belt 18 when the belt unit 80 is detached from the main
body casing 2 is composed by an existing component (i.e. the backup
roller 22) and not a dedicated component.
[0094] In this respect, the urging towards the outer side of the
belt that is generated by the spring 84 is released by the first
supporting member 82 being pushed to the inner side of the belt
unit 80 by the urge releasing protrusion 86. In addition, the
backup roller 22 is urged towards the cleaning roller 21 by the
spring 85 and the second supporting member 83. Although the urging
force of the spring 84 is less than that of the coiled springs 72
based on a relationship between the space and the required load,
this is simply because a large force is not required. It should be
understood that there is no active reason requiring the force to be
small.
<Additional Illustrative Aspect>
[0095] A further illustrative aspect of the image forming apparatus
will now be described with reference to FIGS. 9 and 10.
[0096] FIG. 9 is an enlarged partial side sectional view showing a
state in which a belt unit 90, according to this aspect, is
detached from the main body casing 2. FIG. 10 is an enlarged
partial side sectional view showing a state in which the belt unit
90 is mounted in the main body casing 2. In the following
description, structural differences are mainly described with
respect to the previous aspects. Components that have the same
functions as those of the previous aspects are denoted by the same
reference symbols. A duplicate description of these components is
omitted.
[0097] Instead of the fixing member 55 and the spring 57 of the
previous aspect, the belt unit 90 of the current illustrative
aspect comprises urging devices 91 for urging respective transfer
rollers 19 (corresponding to examples of securing members) in an
outward direction. Urging devices 91 are provided at positions on
the left and right ends of each transfer roller 19. Each urging
device 91 respectively comprises a first supporting member 92, a
second supporting member 93, a spring 94, and a spring 95.
[0098] The first supporting member 92 is provided such that it can
rotate around a mounting shaft 92A arranged in the belt frame 50.
The first supporting member 92 is urged upward (i.e., a counter
clockwise direction as viewed in FIGS. 9 and 10) by the spring 94.
The first supporting member 92 includes a guidance pin 92B that
extends laterally (i.e., horizontally) below the mounting shaft
92A.
[0099] A mounting shaft 93A is provided at one end of the second
supporting member 93 and is arranged in a rotatable condition below
the mounting shaft 92A of the first supporting member 92. The other
end (i.e., free end side) of the second supporting member 93
supports a transfer roller 19 in a freely rotatable condition. The
second supporting member 93 is urged upward (i.e., a counter
clockwise or anti-clockwise direction as viewed in FIGS. 9 and 10)
by the spring 95 provided between the first supporting member 92
and the second supporting member 93. The second supporting member
93 contacts against a stopper part 92C of the first supporting
member 92 in a state in which an external force is not applied to
the second supporting member 93.
[0100] A link lever 97 (corresponding to an example of an urge
releasing device) is provided in the main body casing 2 that can
slide backward and forward. An operation part 97A is provided in a
protruding manner on the undersurface at the front end of the link
lever 97. On the top surface of the link lever 97, pin engaging
parts 97B are provided in a condition such that they can engage the
guidance pins 92B of each first supporting member 92. The pin
engaging parts 97B may contain a corresponding guidance pin 92B
from the front and rear directions.
[0101] As shown in FIG. 9, in a state in which the belt unit 90 is
detached from the main body casing 2, the transfer rollers 19 are
held in a position in which they project upward further than the
top surface of the belt frame 50 due to the urging devices 91. At
this time, each of the transfer rollers 19 is pressed against the
inner surface of the conveyor belt 18 due to the urging of a
corresponding spring 94. As a result, the conveyor belt 18 is
stretched without any excessive slackness. Also, the slide member
51 that supported the bearing device 16A of the tension roller 16
is pressed to a rear end position in its range of movement by the
conveyor belt 18.
[0102] When the belt unit 90 is mounted in a normal position in the
main body casing 2, each guidance pin 92B engages with a respective
pin engaging part 97B of the link lever 97. Thereafter, when an
operating force is applied to the operation part 97A so as to slide
the link lever 97 backward, each guidance pin 92B moves to the rear
side. As a result, the first supporting members 92 and the second
supporting members 93 rotate downward around the mounting shafts
92A. The transfer rollers 19 descend to withdraw almost completely
below the top surface of the belt frame 50 (e.g., the top ends of
the transfer rollers 19 may project slightly above the top surface
of the belt frame 50).
[0103] Thereby, the urging due to the urging devices 91 is released
with respect to the conveyor belt 18. Since the tension roller 16
receives the elastic restoring force of the coiled springs 72 and
is urged toward the front side, a predetermined operating tensile
force is imparted to the conveyor belt 18. Subsequently, when the
process cartridges 26 are mounted above the belt unit 90, each of
the transfer rollers 19 is pushed down to a predetermined degree by
a respective photosensitive drum 31. Additionally, the transfer
rollers 19 are pressed into contact with the photosensitive drums
31 due to the urging of the springs 95.
[0104] As previously described, according to the present aspect,
the structure of the belt unit 90 is simplified since the securing
member is composed by existing components such as the transfer
rollers 19, and not a dedicated component.
<Additional Illustrative Aspect>
[0105] An additional illustrative aspect of the image forming
apparatus will now be described with reference to FIGS. 11 and
12.
[0106] FIG. 11 is a side sectional view showing the schematic
configuration of a laser printer 100 as an image forming apparatus
of the present aspect. FIG. 12 is a side sectional view of the
laser printer 100 in a state in which process cartridges 26 and a
belt unit 101 are detached there from. In the following
description, the right side in FIGS. 11 and 12 is taken to be the
front side.
[0107] The laser printer 100 of the present aspect is a tandem-type
color laser printer that employs an intermediate transfer method
using an intermediate transfer belt 106. In the following
description, components having substantially the same functions as
those of the previous aspects are denoted by the same reference
symbols. A duplicate description of these components is
omitted.
[0108] The laser printer 100 comprises a belt unit 101 that is
detachable from the main body casing 2. The belt unit 101 comprises
a belt frame 102 that is composed by an insulative synthetic resin
material. The belt frame 102 forms a substantially triangular shape
when viewed from the side.
[0109] A driving roller 103, a tension roller 104 (corresponding to
an example of a securing member), and a driven roller 105, are
respectively provided at the front end, the rear end, and the lower
end, of the belt frame 102. The intermediate transfer belt 106 is
stretched by these rollers 103, 104, and 105. Underneath the belt
unit 101, a secondary transfer roller 117 is arranged, facing the
driven roller 105 at the lower end of the belt frame 102, such that
the intermediate transfer belt 106 is sandwiched between the
secondary transfer roller 117 and the driven roller 105. The laser
printer 100 is configured so that a secondary transfer bias is
applied between the secondary transfer roller 107 and the driven
roller 105.
[0110] The laser printer 100 is configured such that the four
colors of toner images, which are respectively formed by four
photosensitive drums 31, are temporarily transferred onto the
intermediate transfer belt 106. Thereafter, when a sheet 4 passes
through the position where the secondary transfer roller 117 is
pressed into contact with the intermediate transfer belt 106, the
toner images that were transferred onto the intermediate transfer
belt 106 are transferred onto the sheet 4.
[0111] At the rear end of the belt frame 102 is provided a slide
member 107 that can slide forward and backward. Bearing devices
104A, which are mounted at both ends of a shaft of the tension
roller 104, are supported by the slide member 107. The slide member
107 is urged in an outward (backward) direction by a spring
108.
[0112] In a state in which the belt unit 101 is mounted in the main
body casing 2, as shown in FIG. 11, the conveyor belt 18 is
stretched by a predetermined operating tensile force since the
tension roller 104 receives an urging force from the coiled springs
72 and the springs 108 such that it is urged in an outward
direction.
[0113] Further, in a state in which the belt unit 101 is detached
from the main body casing 2, as shown in FIG. 11, the conveyor belt
18 is held in a state in which it is stretched without a
significant amount of slackness since the tension roller 104
projects outward due to the outward urging of the springs 108. At
this time, the tensile force imparted to the conveyor belt 18 by
the springs 108 is designed to be less than the operating tensile
force imparted by the coiled springs 72 when mounting the belt unit
101 in the main body casing 2. Therefore, the rigidity of the belt
frame 102 can be reduced in comparison to a case in which an urging
device is provided that imparts a tensile force to the belt unit
101 that is equal to the operating tensile force of the coiled
springs 72. Consequently, miniaturization of the belt unit 101 is
enabled.
<Other Aspects>
[0114] The present invention is not limited to the illustrative
aspects described by the foregoing descriptions and drawings. For
example, the following exemplary aspects are also included within
the technical scope of the present invention. Various changes and
modifications, other than those described below, may be made
therein without departing from the spirit or the subject matter of
the invention.
[0115] (1) In each of the previously described aspects the securing
member was composed by an existing component such as a tension
roller. However, the securing member may also be composed by a
component that is specifically provided for that purpose.
[0116] (2) In each of the previously described aspects the belt of
the belt unit was configured as a conveyor belt or an intermediate
transfer belt. However, the present invention may also be applied
to an image forming apparatus in which a belt is configured as a
photosensitive belt.
* * * * *